The present invention relates to a biodegradable crosslinked polymer having a chelating effect and a function to disperse an oily substance and an inorganic substance hardly soluble in water as well as showing excellent dispersion performance into water and further, the invention relates to a process for producing the crosslinked polymer. Still further, it relates to use of the crosslinked polymer, especially, relates to detergency enhanced by combining this crosslinked polymer with a detergent composition and, thence, a builder excellent in biodegradability and a detergent composition containing this builder.
In addition, it relates to a biodegradable medicine, which may be used involving discharge into environment at a final stage, such as a fiber-treating agent, an inorganic pigment dispersant and a water treatment agent.
When a builder is combined with a detergent, the chelating and dispersing effects of the builder increase detergency of the detergent.
Preferable builders conventionally and widely used from viewpoints of performance, safety and price are condensed phosphates such as sodium tripolyphosphate and the like. However, since phosphorous compounds of these types are an origin of eutrophication for a river, lake, marsh and the like, their use has been limited in recent years and substitution of them is in rapid progress.
At present, instead of the condensed phosphates such as sodium tripolyphosphate and the like, zeolite which is not problematic in the eutrophication and safety is used. However, the zeolite is not enough in builder performance and also, it is insoluble in water and, thence, its combination with a liquid type cleaner is not possible and precipitation with the washing may occur.
On the other hand, instead of the above-described inorganic compounds, an organic compound, for example, a polyelectrolyte such as a polyacrylate and polymaleate has been used as a builder. The polyacrylate and polymaleate are superior in the builder performance, but there is a defect that they are poor in biodegradability.
In Japanese Official Patent Provisional Publication, showa 54-52196, a polyacetal carboxylate has been proposed as a polymer type builder improved in biodegradability. The polyacetal carboxylate is not economical because of its high material cost and also, the process for producing the carboxylate is complicate and not of practical use. In Japanese Official Patent Provisional Publications, showa 63-305199 and 63-305200 and heisei 1-306411 and 2-36210, a water-soluble polymer made by polymerizing a monomer having at least two of an ethylenically unsaturated double bond has been proposed. A water-soluble polymer of this type, according to studies of the present inventors, is difficult in controlling the molecular structure and contains a considerable proportion of molecules not having a structure suitable to biodegradation, and therefore, there is a problem that this type polymer may contain an ingredient which does not undergo biodegradation at all or may require a long period of time for biodegradation. Graft polymers of polysaccharides with acrylic acid and the like in Japanese Official Patent Provisional Publication, showa 61-31497, and graft polymers of monosaccharides and/or oligosaccharides with acrylic acid and the like in Japanese Official Patent Provisional Publication, showa 61-31498, have been proposed. In the graft polymers of these types, only the parts of polysaccharides, monosaccharides and oligosaccharides undergo biodegradation, but the graft parts due to acrylic acid and the like have large molecular weights and do not undergo biodegradation.
Like this, all of the forementioned polymers have defects and, therefore, any polymer satisfactory enough has not yet found.
In the field of fiber-treating agents, a polyacrylate has been conventionally used by combining it with a chelating agent to elevate dispersing performance. In the field of inorganic pigment dispersants, a polyacrylate and a maleic acid-acrylic acid copolymer salt have been used to decrease the viscosity of a solution of dispersed slurry and to elevate the stability of viscosity. In the field of water treatment agents, a polymer such as polyacrylate, polymaleate and the like has been used instead of the conventional phosphine-based medicine as a scale suppressant of calcium carbonate.
However, these polycarboxylic acid-based polymers show good performance in various kinds of use, but they have a defect, that is poor in biodegradability.